CN104520537B

CN104520537B - Movable turbine blade

Info

Publication number: CN104520537B
Application number: CN201380041213.2A
Authority: CN
Inventors: 拉斐尔·杜皮耶; 约瑟兰·巴瑟瑞; 文森特·弗朗西斯·布莱
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2012-08-03
Filing date: 2013-07-19
Publication date: 2020-01-17
Anticipated expiration: 2033-07-19
Also published as: CA2880829C; RU2015107176A; FR2994211B1; WO2014020258A1; CA2880829A1; BR112015002350A2; FR2994211A1; RU2642948C2; EP2880265A1; US9920632B2; BR112015002350B1; US20150218950A1; EP2880265B1; CN104520537A

Abstract

The invention relates to a movable blade (1) of a low-pressure turbine, comprising a foot (10) and a vane (30), the vane (30) having an upper surface (31) and a lower surface (32), the foot (10) comprising a strut (11) connecting the vane (30) and the foot (10); the blade (1) is characterized in that: -forming the pillar (11) such that the cross section of the pillar has: a first straight portion (14), a second curved portion (15) and a third straight portion (16), the curved portion (15) having an outer face (18) matching the contour of the upper surface (31) of the tab (30) and an inner face (17) matching the contour of the lower surface (32) of the tab (30).

Description

Movable turbine blade

Technical Field

The field of the invention relates to movable blades in low-pressure turbines of turbomachines.

The invention relates more particularly to a specific arrangement of the movable blade feet of a low-pressure turbine.

Background

Conventionally, as shown in fig.1, the movable blade 1 of a low-pressure turbine comprises three components: a lower portion referred to as the foot 10, an upper portion referred to as the heel 20, and an intermediate portion formed by the flap 30.

The foot 10 of the movable blade 1 comprises three functional components:

a strut 11, connecting between the fins and the foot 10;

balls 12, which make a mechanical connection between the movable blades and the turbine rotor disc;

a spoiler 13, reducing the leakage, to maximize the efficiency of the low pressure turbine.

The strut 11 is an important part of the foot 10, since it maintains the mechanical connection between the fins 30 and the foot 10, which foot 10 is fixed to the rotor disc and thus in a position where high mechanical stresses exist.

Conventionally, the movable blades of low-pressure turbines have struts that are approximately straight, corresponding to the shape of the top of the bulb (i.e., the top of the dovetail).

However, such struts do not meet the required mechanical requirements in some geometrical configurations, in particular in the presence of complex-shaped fins.

In this case, curved struts have been developed which have the same shape or more precisely the same profile as the fins to provide maximum overlap between the strut 11 and the fins 30 or more precisely between the profile of the cross section of the strut 11 and the cross section profile of the fins 30.

The development of this type of strut configuration has resulted in uniform stresses in this part of the blade, but has also resulted in an increase in the mass of the blade and hence of the low pressure turbine. It will be clearly understood that an increase of a few grams in the mass of the movable blades will have the consequence of increasing the mass of the entire turbine, which comprises a plurality of stages, each formed by a few hundred movable blades, by a few kilograms.

Disclosure of Invention

In this context, the invention discloses a movable low-pressure turbine blade which is lighter in weight than a movable blade according to the prior art and which can withstand the imposed mechanical stresses.

To achieve this object, the invention discloses a movable blade for a low-pressure turbine, with a foot and a vane, the vane having an outer face and an inner face, the foot having a strut connecting the blade and the foot; the blade is characterized in that the strut is formed such that the cross section of the strut has a first straight portion, a second curved portion and a third straight portion, the curved portion having an outer face corresponding to the outer contour of the airfoil and an inner face corresponding to the inner contour of the airfoil.

With the invention, the mass of the turbine is reduced while maintaining good mechanical strength.

Advantageously, the straight portion is located on each side of the curved portion.

The lengths of the different sections are adjusted, in some cases, according to the mechanical properties required. Thus, the length of the curved portion relative to the straight portion can be varied to further improve the mechanical properties of the foot.

Advantageously, the curved portion is defined such that the cross section of the curved portion is superimposed on the cross section of the base of the fin with an overlap of more than 95%.

Advantageously, each of said portions of the strut has a constant thickness.

Another object of the invention is a low-pressure turbine with a plurality of movable blades according to the invention.

The invention will be better understood upon reading the following description with reference to the drawings, a list of which is given below.

Drawings

Fig.1 described above shows movable blades of a low-pressure turbine.

Fig.2 schematically shows a sectional view in a cross-sectional plane of a strut of a movable vane according to the invention.

Fig.3 shows a superposition of the section shown in fig.2 and the section of the airfoil of the blade according to the invention on a cross-sectional plane parallel to the cross-sectional plane of the strut.

Detailed Description

With reference to fig.2, the strut 11 has a cross section divided into three distinct portions:

a first straight portion 14;

a second curved portion 15;

a third portion 16, which is again straight.

The curved portion 15 is located between the two

straight portions

14 and 16. Each

portion

14, 15, 16 has a constant thickness.

As shown in fig.3, the geometry of the strut 11 of the blade according to the invention comprises a curved portion 15 which matches a part of the contour 35 of the bottom of the airfoil 30 of the blade shown in dashed lines in fig. 3. The bottom of the flap means the part of the flap that connects the struts.

The two profiles at the curved portion 15 are identical, in other words the outer face 18 of the curved portion 15 has the same profile as the outer face 31 of the bottom of the tab 30 (shown in fig. 1), and the inner face 17 has the same profile as the inner face of the bottom of the tab 30 (fig. 1). Advantageously, the portion 15 has the same thickness as the bottom of the respective tab 30, so that the two profiles overlap.

The length of the

different portions

14, 15 and 16 of the strut 11 may vary and vary according to the mechanical properties required. If a better resistance to imposed mechanical stresses is required of the foot 10 of the blade, the proportion of the curved portion 15 can be increased at the expense of the

straight portions

14, 16. Thus, different lengths can be adjusted and should be optimized according to the desired weight/resistance ratio. The shape of the post 11 is determined, for example, by using successive iterations of CAD models and thermo-mechanical calculations.

The struts are thus developed such that the bent portions 15 overlap the cross section of the fins 30 by at least 95%, and advantageously by 100%. For example, a complete overlap of the order of 65% to 75% between the airfoil section and the strut section may give sufficient mechanical robustness for applications in the field of low-pressure turbines, while producing savings in terms of mass.

According to one embodiment in the field of low-pressure turbines, the profile of the strut comprises:

a first straight portion 14 having a length of 2 mm;

a curved portion 15 having a chord length of 10mm at the outer contour and 8mm at the inner contour;

a third straight portion 16 having a length of 4mm at the outer face and a length of 6mm at the inner face.

The thickness of the profile of the pillar is constant and equal to 2 mm. Thus, with this profile, the overlap ratio of the strut and the flap base is 85%.

Claims

1. A movable blade (1) of a low pressure turbine having a foot (10) and a vane (30), the vane (30) having an outer face (31) and an inner face (32), the foot (10) having a strut (11) connecting the vane (30) and the foot (10); the blade (1) is characterized in that: -forming the strut (11) such that its cross section has a first straight portion (14), a second curved portion (15) and a third straight portion (16), the second curved portion (15) having an outer face (18) and an inner face (17), the outer face (18) having the same profile as the outer face (31) of the bottom of the tab (30), the inner face (17) having the same profile as the inner face (32) of the bottom of the tab (30).

2. The movable blade (1) of a low-pressure turbine according to claim 1, characterized in that: the first straight portion (14) and the third straight portion (16) are located on each side of the second curved portion (15).

3. The movable blade (1) of a low-pressure turbine according to claim 1, characterized in that: the length of the second curved portion (15) is adjusted according to the desired mechanical properties.

4. The movable blade (1) of a low-pressure turbine according to claim 1, characterized in that: the second curved portion (15) is defined such that a cross section of the second curved portion (15) overlaps a cross section of the fin (30) with an overlap of more than 95%.

5. The movable blade (1) of a low-pressure turbine according to one of claims 1 to 4, characterized in that: each of said first (14), second (15) and third (16) straight portions has a constant thickness.

6. Low-pressure turbine of a turbomachine, characterized in that: comprising a plurality of movable blades (1) of a low-pressure turbine according to one of claims 1 to 5.